Pre Surgical Imaging of Fistula in Ano

Abstract:

In 1976,
Parks, Gordon and Hardcastle published their article entitled ‘A classification
of Fistula- in ano.’ Their classification was based on the identification of
four types of fistula: inter sphincteric, trans sphincteric, supra sphincteric
and extra sphincteric. An intersphincteric fistula runs downwards between the
internal and external sphincters. The trans sphincteric fistula runs from the
intersphincteric space, through the external anal sphincter into the
ischiorectal space. The supra sphincteric fistula runs upward between the
internal sphincter and external sphincter and then bends around the pubo
rectalis muscle and penetrates the pelvic floor, to traverse downwards through
the ischiorectal fossa.

An extra sphincteric
fistula passes through the external anal sphincter and then branches out into
two tracks- one extending cephalad penetrating the pelvic floor and finally
ending in rectum and the other extending caudally ending in the external
opening. Although this classification does not take into account the
circumferential extend of the disease it is widely used because of its
simplicity. Another reason is that this classification relates the anatomical
relation of the fistulous track to the anal sphincters which is relevant for
the choice of treatment.